The long term objectives of this project are to understand the molecular basis of neural structure and development. This is essential not only for an understanding of the normal functioning of the central nervous system but also for an understanding of the wide variety of developmental and degenerative abnormalities that can affect neural tissue. This proposal seeks to characterise a series of cell-type specific molecules that have been identified with monoclonal antibodies and to use culture systems to study the mechanisms controlling the expression of these molecules. Monolayer and aggregate cultures of rat retina and other CNS areas will be set up from animals of various ages. The expression of defined cell-type specific molecules by particular cell types has already been characterized in these culture systems and is probably not dependent upon factors extrinsic to the retina. Expression of these molecules will be monitored after various treatments that modify the composition and possibilities for cellular interactions. Modification of cell density, removal of cell types by antibody-mediated cytotoxicity and growth of single cells in microcultures will all be carried out. These experiments will be interpreted in terms of the role of particular cell types upon the differentiation of other cell types. Some cell types have been found to take on a characteristic morphology in culture. The role of substrate adhesion, cell density and cellular interactions will all be examined to determine whether this is controlled by extrinsic factors or is a part of an intrinsic developmental program. The cell-type specific molecules will be characterised by standard biochemical methods to measure molecular weight and patterns of glycosylation. More detailed analysis will involve isolation of cDNA clones from existing plasmid and bacteriophage libraries. The cloned DNA fragments will be used both for biochemical analysis and for developmental studies to define the times of gene expression in vivo and in vitro. The cDNA libraries will also be screened to detect both cell-type and developmental-stage specific gene transcripts. These will provide the starting material for the studies of nucleotide sequences that may play a role in the regulation of gene activity during neural development.